1. Field of Invention
The present invention relates generally to web inspection systems and more specifically to smart camera systems for detecting flaws and defects of web material.
2. Background
A “web” is a flat material produced continuously in large quantities and at very high rates. Typical web materiel includes fabrics, sheet metal, paper, and non-woven plastic, etc. Inspection of the web material surface is required during production to find flaws and defects. Failure to detect these flaws and defects may result in thousands of feet of unusable web material. Thus, there exists varying methods of web inspection from manual inspection and sampling to image acquisition, processing and analysis.
FIG. 1 illustrates a traditional system 10 for web inspection utilizing line scan cameras 22 positioned above a web 12. Typically, two types of sensor technology, charge coupled device (CCD) or CMOS, are utilized. While CMOS technology allows the signal processing electronics to be on the same chip as the sensor, CCD sensor technology offers advantages superior imaging quality as compared to CMOS sensors, and stand alone components. Continuing with FIG. 1, high bandwidth camera-specific data cables 34 are required to transfer data from the line scan cameras 22 to a vision processor 32. A typical high bandwidth data stream transfer is forty (40) million pixels per seconds, i.e., 500 Mbits per second for pixels of eight (8) bits.
The megapixel data stream is transferred over the camera-specific cables 34 to frame grabber modules 24 in the vision processor 32. Frame grabber modules 24 utilize standard integrated circuit (IC) boards to digitize an analog video stream image from a line scan camera 22. The digitized images, represented by arrays of numbers, are streamed to pipeline vision processors 26 for real time preprocessing. The pipeline vision processors 26 utilize dedicated image processing boards for data and image analysis that may be different for various webs. For example, a pipeline vision processor 26 may be configured to extract specific information from an image. The processed images from each of the pipeline vision processors 26 are sent to an image analyzer processor 28 that further analyzes and processes an image of the full width of the web 12. The web inspection system 10 of the prior art may further include an image buffer board 30 for data storage. The vision processor 32 of the prior art requires a large chassis to house the IC boards of the frame grabber modules 24, the pipeline vision processors 26 the image analyzer processor, and the image buffer 30.
The processed image from the vision processor 26 is sent to a host computer 14 for display on the graphical user interface (GUI) of the host computer 14. Also connected to the host computer 14, is a defect marker 18 and an encoder 16. The encoder 16 sends information to the host computer 14 including the speed of the web 12. The web 12 typically moves over a rotary device driven by a shaft and roller that produce pulses per unit distance. The host computer 14 utilizes this information to determine the size and position of a defect. The host computer 14 may also include a database input/output board to control a defect marking system 18, and other peripheral device connections 20.
The web inspection systems 10 of the prior art present several disadvantages. As described above, prior art web inspection systems 10 require a high number of components that are supplied by many different manufacturers, thus presenting compatibility problems. Integration of the components is difficult and expensive, and the resulting system is often difficult to configure and use. The prior art web inspection systems 10 typically have large footprints and require racks or large custom boxes of boards for parallel processing. These extra racks of equipment and the operator console, or host computer 14, must be out on the floor and relatively close to the web equipment 12 due to the constraints on the length of connecting cables which must transmit a large bandwidth of data. For example, custom shielded cables are required to connect components to protect the video signal from picking up background noise. The requirement of proprietary cables and the large bandwidth transmission of the high speed raw image data from the cameras limits and/or preempts the use of standard factory ethernet cables to link all components and factory computers.
A further disadvantage of the prior art web inspection systems 10 as shown in FIG. 1 is the low mean time between failure due to the number of components. In addition, a web inspection system 10, as shown in FIG. 1, is an unbalanced architecture, meaning that one component in the system often limits the performance of the system. For example, high speed data sent over cables 34 may jam processing in the vision processing box 32. Also, high defect rates may cause overload occurrences in the image analyzer processor 28. Expansion of an unbalance architecture to add more capability is usually very expensive, and the system 10 is often already maximized, e.g. the rack holding the equipment cannot accept more boards. Another drawback of the non-robust web inspection system 10 of the prior art is that the system 10 is not easily scalable. Therefore, if a customer requires the detection of defects that are half the size that the current system 10 is capable of detecting, more cameras may be added, but the system 10 cannot be configured to accept more pipeline vision processors 26 and/or a second image analyzer 28.
Thus there exists a need for a balanced and robust web inspection system that is easily integrated with an existing manufacturing Ethernet, and is capable of detecting a high rate of web flaws and defects.